Docker Series — Part 7: Custom Networks, IPAM, and Multi-Container Communication

Welcome to Part 7 of the Docker: Basics to Advance series.
Today’s session is all about building real networking control using Docker’s built-in tools — from creating your own networks to running WordPress + MySQL with custom IPs, names, and communication paths.

Docker is Not Just for Containers — It’s Infrastructure Too

When I started using Docker, I thought it was just a tool for running containers. But as I went deeper, I realized — Docker also builds the entire network and storage infrastructure behind the scenes.

From bridges to IPAM (IP Address Management), Docker offers the kind of control you'd expect from full-scale cloud providers.

You can see this using:

docker info

Look at the plugins section — you’ll see Network: bridge, host, macvlan, overlay...
Docker is acting as a virtual router + switch + DHCP + DNS all at once.

What Happens When You Launch a Container?

• Docker assigns an IP to your container from a subnet range.

• It attaches it to the default bridge network.

• It creates a virtual network card for the container (eth0).

• The container can ping the internet, but not the other way around (because of NAT).

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Understanding Bridge Networking in Docker

Docker creates a default bridge network that acts like a combo device:

• It works like a Layer 2 switch (connects systems on the same subnet)

• It behaves like a router when containers are on different networks

You can inspect this using:

docker network inspect bridge

Inside the output, you’ll see details like:

• Subnet range (172.17.0.0/16)

• IPAM settings

• Containers attached to this network

• Gateway IP

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Creating a Custom Docker Network

Now we go from passive user to network architect
Let’s create our own custom network:

docker network create --driver bridge --subnet 10.1.2.0/24 lwnet

Check it:

docker network ls

You’ll now see lwnet with your chosen subnet. Docker has now created a new isolated network.

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Launching Containers in a Custom Network

docker run -dit --name os4 --network lwnet ubuntu:14.04

Now run:

docker exec -it os4 ifconfig

You'll see:

eth0 → 10.1.2.2

Note:

• 10.1.2.0 is the network

• 10.1.2.1 is the gateway

• 10.1.2.2 is the container’s IP

You’ve now got control over the IP range, and containers can ping each other by name, thanks to Docker’s IPAM + DNS support.

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Deploying WordPress + MySQL in a Custom Docker Network

This is where it gets fun — let’s connect real apps in our network.

Step 1: MySQL Database Container

docker run -dit --name mydb1 --network lwnet \
-e MYSQL_ROOT_PASSWORD=redhat \
-e MYSQL_DATABASE=mydb \
-e MYSQL_USER=jibbran \
-e MYSQL_PASSWORD=redhat \
-v /mydata:/var/lib/mysql \
mysql:latest

Step 2: WordPress Application Container

docker run -dit --name mywp1 -p 8080:80 --network lwnet wordpress:latest

Step 3: Open in Browser

Go to http://<your-server-ip>:8080
During setup, connect WordPress to:

• DB Host: mydb1

• DB Name: mydb

• Username: jibbran

• Password: redhat

WordPress and MySQL are now connected via container name, not IP, inside a custom Docker network!

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Key Takeaways

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Why This Matters

Using custom Docker networks gives you:

• Better security and isolation

• Reliable name-based communication

• Control over IP schemes (like in cloud infra)

• Flexibility for multi-container applications

This is how real production setups are made — controlled, connected, and ready to scale

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Have questions about Docker networking, IPAM, or multi-container deployment?
Drop a comment or DM — let’s grow together!